1. Field of the Invention
The invention generally relates to an image sensor, and more particularly, to a sampling device and a sampling method of an image sensor.
2. Description of Related Art
Along with the progress of semiconductor and optoelectronic technology, our lives are currently full of more and more digital cameras, digital monitors or digital video cameras. The photograph apparatus such as digital camera, digital monitor or digital video camera requires a photosensitive component to convert a sensed light signal into an electric signal and then to output the electric signal to a rear-stage circuit for image processing. In general speaking, a photosensitive component is mostly a charge coupled device (CCD) or a CMOS image sensor, in which the CCD has better image quality than that of a photograph apparatus using a CMOS image sensing element.
Currently, several techniques related to the image sensing element are provided. For example, U.S. Pat. No. 7,091,466 discloses an image sensing circuit, which enables a rear-stage circuit to read the electric signals of a plurality of photosensitive components during one time so as to enhance the intensity of the electric signal and make the rear-stage circuit more easily sense the electric signal. However, the scheme requires an additional circuit to achieve the function, and thus the volume of the apparatus and the production cost are increased. In addition, the above-mentioned image sensing circuit has poor anti-thermal-noise capability. Since the electric signal read by the rear-stage circuit thereof is also a non-linear signal, the reading operation is easily affected by noise. In particular, it is unable to add signals linearly when a plurality of photosensitive components are required to be read for one time.
Additionally, U.S. Pat. No. 5,898,168 discloses an image sensing circuit, which utilizes a rear-stage circuit to read the voltage value produced by a photosensitive component according to the light signal. However, when the light signal is too weak so that the voltage value is not high enough, the rear-stage circuit of the image sensing circuit is easy to wrongly read signals. In addition, since the above-mentioned image sensing device provides a voltage value to the rear-stage circuit, it is difficult to read out a plurality of voltage values during one time in circuit implementation, which can make the rear-stage circuit read out a stronger electric signal so as to reduce the probability of the above-mentioned wrongly reading.